From: Ilpo Järvinen <ij@kernel.org>
Date: Thu, 11 Sep 2025 11:06:29 +0000 (+0200)
Subject: tcp: reorganize SYN ECN code
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=449144f4d5f284c038c57bd7ea54c0d4b7ca766d;p=users%2Fhch%2Fmisc.git

tcp: reorganize SYN ECN code

Prepare for AccECN that needs to have access here on IP ECN
field value which is only available after INET_ECN_xmit().

No functional changes.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250911110642.87529-2-chia-yu.chang@nokia-bell-labs.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e180364b8dda..54b8faa3ad95 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -350,10 +350,11 @@ static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
 	tp->ecn_flags = 0;
 
 	if (use_ecn) {
-		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
-		tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168);
 		if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
 			INET_ECN_xmit(sk);
+
+		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
+		tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168);
 	}
 }